Number portability (NP) gives telephone service subscribers the ability to change local service providers without changing directory numbers. As used herein, the term “number portability” includes service provider portability, which allows subscribers to change local telephone service providers without changing directory numbers; service portability, which allows subscribers to change from one type of service to another (e.g., analog to integrated services digital network (ISDN) without changing phone numbers; geographic portability, which allows subscribers to move from one physical location to another without changing directory numbers, or any other type of service-related portability in which a subscriber desires to keep the same directory number.
In a non-NP environment, a telephone number performs two basic functions: it identifies the customer, and it provides the network with information necessary to route a call to that customer. Number portability solutions separate these two functions, and thereby provide the means for customers to keep the same directory number when changing one of the above-mentioned aspects of telephone service. By separating these two functions, NP gives service provides the flexibility to respond to pricing and service changes offered by rival carriers. Accordingly, it is anticipated that NP will promote local-exchange competition, which in turn will benefit all customers, as has already been the case with the long-distance market. As NP solutions are implemented, competition in the local-exchange market is expected to drive down the cost of service, encourage technological innovation, stimulate demand for telecommunications services, and boost economic growth.
While intelligent network (IN) and advanced intelligent network (AIN) solutions to the problem of number portability exist, these solution are query and response based. Consequently, end office (EO) and mobile switching center (MSC) facilities must be upgraded to support such NP functionality, which is expensive both from a financial standpoint as well as a resource management perspective. For example, one wireless network operator in the United States has recently estimated that approximately 20% of their MSC resources are currently being monopolized by NP query/response related processing.
Triggerless number portability (TNP) support gives service providers a method to route calls to ported numbers without having to upgrade their signaling switch (EO or MSC) software. With existing trigger based IN/AIN NP solutions, service providers are required to modify their EO and MSC equipment so as to incorporate the ability to generate and receive NP query and response messages, respectively. An internally generated NP trigger will cause an EO/MSC node to launch an NP query to an NP database that resides in the signaling network. The EO/MSC node routes a call based on an location routing number (LRN) returned from NP database lookup. Triggerless number portability routes calls to ported numbers without requiring this query and response mechanism.
Commonly-assigned, co-pending U.S. patent application Ser. No. 09/503,541, entitled Methods and Systems For Routing Signaling Messages Associated With Ported Subscribers In A Telecommunications Network (hereinafter, the “TNP Patent Application”), the disclosure of which is incorporated herein by reference in its entirety discloses a triggerless number portability solution. The triggerless NP solution described in the TNP Patent Application reduces the need for updates or upgrades to end offices or mobile switching centers in a network. Instead, an ISDN user part (ISUP) initial address message (IAM) sent from an EO or MSC is intercepted by a triggerless-NP-equipped signal transfer point or signaling gateway routing node and is modified to include the appropriate LRN if the call is to a ported number.
One problem with conventional triggerless number portability solutions is inefficient trunk utilization. FIG. 1 illustrates an exemplary wireline communication network and messaging intended to illustrate a conventional TNP solution. In the illustrated example, wireline communications network 100 includes an originating EO 102 associated with a calling party 104, two access tandem switches 105 and 106 (e.g., CLASS 4 offices), an STP 108 with a TNP subsystem 110, a donor EO 112, a recipient EO 114, and a called party 116 that has been ported from the donor EO to the recipient EO. The dashed lines in FIG. 1 indicate signaling communication links, and the solid lines indicate voice trunks.
Messages C1 through C6 represent ISUP signaling that occurs during the course of call setup (e.g., IAM messages). In the scenario illustrated in FIG. 1, originating EO 102 uses it's internal routing data to address the call setup message to donor EO 112, because originating EO 102 is not aware that the called party has been ported. As such, originating EO 102 selects and reserves a voice trunk (trunk 1) connected to tandem office 105 and launches a call setup signaling message, C1, which is addressed to tandem office 105.
Message C1 is received by STP 108, which performs a number portability lookup. In this example, the NP lookup at STP 108 reveals that called party 116 has been ported from donor EO 112 to receiving EO 114. Consequently, an appropriate location routing number (LRN) is inserted into the call setup message, and the modified call setup message (C2) is routed to tandem office 104. Tandem office 105 receives message C2, selects and reserves voice trunk 3, and launches call setup message C3. Message C3 is received by STP 108 and through-switched to tandem office 106 as message C4. Tandem office 106 receives the message C4 and launches a call setup message C5, which is routed to receiving EO 114 as call setup message C6.
At this point, a significant shortcoming/inefficiency in this triggerless LNP solution becomes apparent. That is, trunk 1 has already been reserved by originating EO 102 prior to the determination that the called party has been ported and is no longer serviced by donor EO 112. Consequently, tandem office 105 and voice trunks 1, 3 and 4 are involved in the call even though the most efficient/direct voice trunk path would only involve trunks 2 and 4.
Therefore, what is needed is a triggerless NP solution that improves the utilization of voice trunks in a telecommunications network environment.